Electric discharge apparatus



0er- 31, 1939. T. E. FOULKE `2,177,883

' ELECTRIC DISCHARGE APPARATUS Filed Sept. l, 1938 ed E. Fo uLkePatented oct. 31,1939

1 futur-sn,A STATES 1 PATENT orrlcI-:v' j

' d varl-Lluis.l Y i A TedE. Foulke, utley, N. '1., assignor.- by mesneassignmenta'to General Electric Company, a

corporation of New York Application september 1, 193s, :serial No.228,049

, 4 Claims. The present invention relates to electric gaseous dischargedevices generally and in particular todevices having starting means ofthe resonance type. A particular object of the invention is to provide anovel means for throwing a resonance or "semi-resonance starting circuitout of resonance .This circuit, which is disclosedin his pending ofswitches connected with the startingcircuit when the discharge device isinoperative forany reason. Still other objects and advantages of myinvention will appear from ,the following detailed specification, o rfrom an inspection of the accompanying drawing.

The invention consists in the new and novel combination of elementshereinafter set forth and claimed.

kAn extremely desirable and effective starting and operating circuit forgaseous electric discharge devices of the full-wave rectifying type hasrecently been devised by Harold W. Lord.

` application. Serial No. 197,357, flied March 22, 1938, provides meansof the semi-resonancetype to raise one of the anodes to a muchhigher-potential than the other anode above the cathode potential,whereby the discharge is initiated between the first of these anodes andthe cathode.

The difference in Vanode potentials `which is thus produced results in across-current discharge between these anodes whichis availed of, where atime 'delay is desired to permit heating up ofthe cathode, to operate yatime delay mechanism of the thermostatic type. Switching means operatedby-the main rectified discharge current is ordinarily provided todisconnect this high voltage from the one anode as soon as the dischargetothe cathoderis started. In some cases, as whereI the lead to thecathode' becomes acci'- dentally disconnected, or where the cathode haslbecome deactivated, so that the discharge to the cathode cannot start,this switching means obl cross currents produce undesired voltagesurges- Also, f

every half cycle, as the current reverses. since .partial resonanceexists during thisstart- `ing period the current drawn from the line isnently desirable. -such as a resistance which' is adapted to be shortvshunt in the anode 'discharge circuit.

two delay means is also preferably so coordinated vthat the'circuit' isderesonated, incase the main discharge is not earlier initiated, priorto -the the first closing thereof. Due to Ithis novel means materiallygreater Athan that reguired during normal operation of the lamp, and theheating of the various elements of the circuit is thus relatively high,so that vsome meansof reducingthe wattage input to the device if themain discharge 5 does n ot start within a reasonable time is emi- Whereatime delay device,

circuited by .a thermostat, .ist included in the anode discharge circuitin orderto keep the cross-current discharge between the anodes down to.a very small value, and at. the same time to reduce the anode potentialto a value insuflicient to 'initiate the main discharge untilthe cathodehas had an opportunity to reach a desired elec- 15 tron emittingtemperature, failure .ofthemain discharge to start at the desired timeuponA short circuitlng of this resistance resu1ts.in the recur-A rentopening and closing Aof the thermostatic i l The le- 20 peatedinterruption of this shunt circuit pro' ciucesv unnecessary wear andtear onthe contacts of fthe-delay mechanism, and alsoproduces undesiredvoltage surges. Hence under these circumstances it is desirable to'provide means to lo'ck out the delay mechanism in case the maindischarge` does -not'start within a reasonable time.

I have Adiscovered that all of these' -desiied results are produced bythe use ,fof Yan 'additional delay mechanism. which Lcompletes vacircuit adapted-to deresonate the means by which'the high Apotential forthe one anode is created,'this new circuit preferably providing its ownholding circuit, whereby when onceclosed it will not reopen without'manual intervention. Where a, time delay mechanism is provided for theprotection of the cathode this novel circuit 4also preferablyshortcircuits or -otherwise locks out this delay mechanism to preventrepeated useless operations thereof, and the timing of the reopeningofthe shunt inthe anode circuit after for throwing the circuit out ofitssemi-resonance condition, the 4total impedance' of `the lamp circuitis materially increased, and the line current is correspondinglydec'reased, with a resultant decreasein the heating of the variouscomponents 'of the circuit. Furthermore the wear and tear which wouldotherwise result from Vuseless intermittent openings lof thecross-current circuit ls entirely eliminated. g

For the purpose of illustrating my invention, u

l'IIS I have shown a schematic diagram of a preferred embodiment thereofin the accompanying drawlng.

As shown in this drawing the electric gaseous discharge device or lamp Icomprises a tubular sealed envelope having an activated thermioniccathode 2 at one end thereof and two similar anodes 3 and 4, of carbonor the like, the latter being preferably separated by a baille 5. 'I'helamp which has thus been schematically shown is conveniently of the typedisclosed in my copending application, Serial No. 149,707, filed June22, ,1937, wherein the lamp contains mercury vapor and a starting gas,such as argon, and .wherein the lamp envelope is coated with afluorescent material. y

Before starting, such a lamp has a high resistance and ordinarilyrequires a voltage considerably higher than that of the circuit fromwhich it is supplied to start a discharge therein. Thus a lamp that willoperate with a drop of the order of 100 volts in the arc may require asmuch as 450 Volts between the cathode and an ano'de to .ionize the gasand initiate the arc discharge. The

auxiliary apparatus shown is especially designed to give this startingvoltage and to ballast the discharge in an extremely eicient manner. Thecircuit shown is essentiallythat disclosed by Lord in his co-pendingapplication, referred to hereinbefore, with the addition of a seconddelay element whose action is coordinated with the action of ,theoriginal delay element in a novel manner.

In this circuit the lamp I is supplied from the source "I of singlephase alternating current which for example may be a 60 cycle, 110 voltlighting circuit, through the unitary structure represented at Standcomprising .a combined high reactance transformer and smoothing reactor.The core of the structure comprises two E-shaped members 9 and I0reversely arranged with respect to each other and with correspondinglegs spaced from each other to form magnetic gaps. In the drawing thesegaps are shown for simplicity as air ,gaps but as the apparatus ismanufactured they comprise a suitable non-magnetic material againstwhich the two members are clamped. Between the legs of the member I0 aremagnetic shunts shown at I I thereby increasing the'ux leakage toprovide a higher leakage reactance.

On each of the outer legs of the core structure is a primary windingconsisting of the coil I2, a main secondary winding consisting of thecoil I3 plus the coil I2 thereby constituting an autotransformer and aseparate auxiliary secondary Winding comprising. the coils I4. The endsof the primary, thus-composed of the two cells I2,\are con; nected bythe leads I5 and switch I6 with the opposite sides of the so'urce 'I.The opposite ends of the main secondary, composed of the two coils I2and the two coils I3, connect with the two anodes 3 and 4, one directlyand the other through a relay which will be described hereinafter, and

'the mid-'point lthereof connects with the cathode 2. The'latterconnection includes the conductor I1 and the auxiliary secondary, madeup of the two coils I4, the purpose of which is to supply heatingcurrent to the lamp cathode.

As shown by the vdrawing the magnetic shunts II are arranged adjacentthe upper ends of the primary coils and extend between the outer legs ofthe core structure and the middle leg I8 thereof,

-said shunts being spaced from those legs by magnetic gaps whichpreferably comprise a suitable nonmagnetic material. It will be Seel)that by this arrangement the amount of leakage of the primary flux isgreatly increased since the shunts provide a relatively low reluctanceleakage path,

moreover, an exceptionally high reactance is obtained between the twohalves or coils of the secondary winding because of the magnetic shunteffect thereof, whereby they are virtually isolated from each other.

A capacitor 24, which is used among other purposes to improve the powerfactor of the unit, is connected across the secondary of the transformerin series with a suitable reactance which not only prevents undesiredharmonics but also avoids an undesired decrease in the angle ofcommutation. In the arrangement shown, which is identical with that ofthe aforementioned Lord application, this inductance is furnished by thereactor or choke coil 25 which has the intermediate tap 26 dividing ityinto the two parts 2l and 28, whereby it can function as anautotransformer. The portion 2l is connected in series With thecapacitor 24 across the secondary of the main transformer. The relativeamounts of capacitive inductance in the closed circuit including thesemembers and the leakage reactance between the primary I2 and secondaryI2 and I3 of the transformer is such that a condition of partialresonance is produced therein, with the natural resonance frequency ofthis circuit preferably slightly higher than the frequency of the supplycircuit, as in the ratio of 65 to 60 cycles, for example. Thissemi-resonance condition results, of course, in a relatively largevoltage drop across the coil 21, and in the production of a still highervoltage, by transformer action; across the entire coil 25, and also inan increased potential across the secondary of the main transformer.

The reactor 25 may have any desired core pro-4 vided it is not the sameas the transformer core. It may, however, be of a form that constitutesan incomplete magnetic circuit in itself but, for pur- 'poses ofeconomy, may be arranged adjacent to a part of the transformer corewhich part thereby serves to complete its magnetic circuit. Such a coreconstruction is shown by the E-shape'd member 29 separated from thetransformer core by magnetic gaps 3D.

Inasmuch as the voltage applied between the cathode and either anode,namely the voltage of one half of the secondary, even when augmented bythe semi-resonant condition described, is insuiicient to initiate adischarge in the lamp, a special starting means Vis provided, wherein atstarting the anode 4 is connected to the extended winding 28 of the coil25, whereby a highv potential'difference, sufcient to initiate thedischarge,

ls produced between the anode 4 and cathode 2.

This starting connection is provided by an electro-magnetic switch 32which is normally biased against the contact 34 by the spring 35. Thisswitch'is adapted to be moved away from the starting contact 34 and intoengagement with the running contact 33 by the armature 36 attachedthereto in response to a predetermined value of the uni-directional iiuxpassing the air gap 31 in the middle leg of the transformer core, thisrunenvases-- ning contacta vbeing directly to the opposite end of thetransformer secondary from that connected to the 'anode 3.

Included in the circuitbetweenv the contact n and the .coil 28` is anovel time delay mechanismy ornprising three bimetallic blades 2l, I!and 4l,

o arranged' as to permit electrical contact between the free ends ofadjacent pairs, and the 30 ohms. These elements are so connected lthatthe heaters 4I and 42 are in series in the circuit from the contact 34to the coil 28, with the heater 4 I nearer said contact I4. One end oi'-the heater 4I is connected to the blade 3l and the other end thereof isconnected to the blade il, whereby this heater is short circuited bycontact between the blades 38 and 39. It maybe noted that the blade 38is merely used to compensate lfor changes in ambient temperature, andmay be replaced by'. a fixed contact where such compensation is notrequired.` The end of the coil 42 which is more remote from the coil.201s also connected to the blade 39, while the blade 40 is connecteddirectly i to. the same end of the transformer secondary which isconnected to the anode l. Thus upon establishment of a contact betweenblades I! and 40 a by-pass including lthe coil 2l and heater 42 iisestablished across the condenser 24 which deresonates the startingcircuit, and at the same time provides suilcient current in heater 42 tokeep the blades 39 and 40 ,in contact.

When the switch I6 is rst closed to energize the lamp and thecontrolling apparatus therefor, a discharge does not immediately start,due to the-l inclusion of the high resistance of the heater 4I in thecircuit tothe anode 4. Heating lof the cathode 2 by the secondary I4,howevexyis immer diately started. During the interval while' the cathodeis heating up to the desired 'temperature cross currents pass betweenthe anodes as, are: sult of the high voltage existing therebetween.These cross currents flow through the Aheater 4I,

' which limits them "to a small value, of the order oi' 20 mllliamperes,and the heater 42 in series. The heat produced by this small currentv110W-- ing through the low resistance heater 42 is negli gible, andhence the blade 40 is substantially unailected thereby but this lsamecurrent ilowing through the high resistance heater 4l produces enoughheat to cause the associated blade l! to move upwardly into contact withthe blade il,

after a predetermined'tlme interval o! the order of x 5' seconds haselapsed, this interval being made to `the free end of thetransformersecondary. Under this normal operation the switch $2 opens the circuitthrough the heater 4! before it 'has functioned.

In case the discharge does not start imme-` dlateiy, however, a isevident that after a definite time interval, determined by the thermallag of.'

theblade n and heater u, the blade as wm move away from` the blade 38,reinserting the heater 4I in the circuit, tendingto cause a recurrenceof this cycle of operation. This action of the blade i! isv undesirable,since once the heater 4I has Abeen short clrcuited the' cross currentsinvrcrease to the order of .9 ampere,V and the opening of this circuitbythe thermostatic blade ,39 is not only destructive of the contacts butalso tends to produce undesired voltage surges in the inductivecircuits. This action is, however, eliminated Awith my novel circuit.since '-the increased cross currents, of the order of .9 ampere, flowthrough the heater 42 and provide suiiicient heat to move .the blade 40toward the blade 39, actual. contact being made, incase the maindischarge is not earlier initiated, before the blade ,39 has cooledsumciently to open the shunt across the heater 4I. When the blades 38and 40 are thus in contact the anodes 3- and 4. are short circuited anda circuit is'created from the end of the winding 28 through the heater42, blade 39 and blade 40 to the end of the transformer secondary ofopposite polarity. This connection throws the circuit entirely out ofresonance, thus reducing not only the `voltage applied to the lamp I butalso materially decreasing the wattage drawn from theenergy source II toa value of the order of one third of that drawn initially, with acorresponding reduction in the heating of the various coils. A currentofthe order of 0.4 ampere still ows through the V'heater 42, however,which is suiilcient to keep thevblades 39 and 40 in contact, especiallyvas the -blade 39 cools and moves toward the blade". Since the anodeslland 4 were short clrcuited by the simultaneous contact of the blades n,v39 and 40 thecross currents were eliminated, and hence the lateropening ofthe contact between the blades 3! and 40 does not open acurrent carrying circuit and-hence is of no eil'ect and unobjectionable.'Ihis setting of the various elements of the circuit then continuesuntil the switch I6 is manually opened and the tube I replaced, or thecause of the diiiculty otherwise eliminated.

While so far I have discussed only the case of a lamp having cathodes ofthe type requiring preheating, it is to be understood that my inventionis also applicable to devices using other types .of thermionlc cathode.Thus where no time delay is required to protect the cathode, the heater4| may be permanently short circuited, or as an ployed. When such acathode only requires a` single inlead it would of course be connecteddirectly to the center tap of the windings I2.

Likewise, while I have shown the delay mechanisms asI being of the'thermostatic type it is to be understood that various other types oftime delay mechanism can be substituted therefor without invention. I-tis also to be understood that various other changes,l omissions andsubstitutions, within the scope of the appended claims, may also be madein the structure illustrated without departing from the spirit of myinvention.

I claim as my invention:

1. In combination, an electric gaseous discharge device having at leasttwo electrodes, a circuit connected with said device to create a highvoltage between said electrodes by series resonance at a commercialfrequency, switching means operative only after the elapse ofl a giventime interval after energization of said circuit v to deresonate saidcircuit at said frequency, and means responsive to the discharge currentthrough said device to render said switching means in,- operative uponinitiation of a discharge between said electrodes.

2. In combination, an electric gaseous discharge device having a cathodeand a pair of anodes, a transformer having its ends connected to saidanodes and a midpoint connected to said cathode, the connection betweenone end of said transformer and its associated anode including meansresponsive to a commercial frequency to produce a high voltage byresonance which increases the potential difference between that anodeand the cathode, switching means operative only after the elapse of apredetermined interval after energization of said transformer toderesonatesaid first mentioned means, and means responsive to thedischarge current through said device to render said switching meansinoperative upon initiation of a discharge between said cathode andanodes. A

3. In combination, an electric gaseous discharge device having a cathodeand a pair of anodes, a transformerhaving its ends connected to saidanodes and a midpointl connected to said` cathode, the connectionbetween one end of said transformer and its associated anode includinglmeans responsive to a commercial frequency to produce a high voltage byresonance which increases the potential difference between that anodeand the cathode, switching means responsive to the flow of cross'currents between ,said anodes to deresonate said first mentioned meansafter fiow thereof for a predetermined time in` terval, and meansresponsive to the discharge current through said device to render saidswitching means inoperative upon initiation of a discharge between saidcathode and anodes.

' 4. In combination, an electric gaseous discharge device having acathode and a pair of anodes,

a transformer havingits ends connected to said anodes and a midpointconnected to said cathode, the connection between one end of saidtransformer and its associated anode including means responsive to acommercial frequency to produce a high voltage by resonance whichincreases the potential difference between that -anode and the cathodeand between said anodes,

whereby cross currents are caused to fiow between said anodes, a highresistance in the circuit traversed by'said cross currents, thermostaticmeans responsive to the heat Iproduced by the flow of said crosscurrents through said ,high resistance to short circuit said resistanceafter a predetermined time interval, switching means responsive to theiiow of said cross currents thereafter to short circuit said anodes andto deresonate said voltage producing means at a predetermined time aftersaid thermostatic means has functioned and before. said thermostaticmeans opens the shortcircuit across saidresist ance, and meansresponsive to the ow of the maindischarge current through said device torender said switching means inoperative upon initiation of a dischargebetween said cathode and anodes.

TED E, FOULKE,

